Exhaust system with serially-connected mufflers



Feb. 27, 1968 P. F. JETTINGHOFF EXHAUST SYSTEM WITH SERIALLY-CONNECTEDMUFFLERS 5 Sheets-Sheet l Original Filed Sept.

www-a Feb. 27, 1968 P. F. JETTINGHOFF 3,370,673

' -CONNEGTED MUFFLERS EXHAUST SYSTEM WITH SERIALLY 5 Sheets-Sheet 2Original Filed Sept. 2, 1964 lrrarur/s EXHAUST SYSTEM WITHSERIALLY-CONNECTED MUFFLERS 5 Sheets-Sheet 5 Original Filed Sept. 2,1964 \M llv \\N I .ll il \MM \WW 3N x W6 m m P m qm E 1d a Md W W Feb.27, 1968 P. F. JETTINGHOFF 3,370,573

EXHAUST SYSTEM WITH SERIALLY-CONNECTED MUFFLERS Original Filed Sept. 2,1964 i 5 Sheets-Sheet 5 omuwww United States Patent 3,370,673 EXHAUSTSYSTEM WITH SERIALLY- CQNNECTEI) MUFFLERS Paul F. Jettinghoit, Jackson,Mich, assignor to Walker Manufacturing Company, Racine, Wis., acorporation of Delaware Original application Sept. 2, 1964, Ser. No.393,864.

Divided and this application Apr. 18, 1967, Ser.

1 Claim. (Cl. 181-35) ABSTRACT OF THE DISCLOSURE A small, highlyeffective exhaust mufller is provided by the use of three longitudinalpartitions (which may be fabricated from a single piece of metal) thatsubdivide the interior of a housing into three series connected gaspassages for main gas flow. The partitions are louvered for secondarygas flow across the gas passages and the resulting acoustic interferenceand turbulence acts with other attenuating effects in the mother tosilence a wide range of frequencies. A complete exhaust system using themufiier is disclosed.

Cro's reference to .related application This application is a divisionSer. No. 393,864 filed Sept. 2, 1964.

Summary of the invention The invention relates to mufflers of the typethat are used in the exhaust systems of internal combustion engines. Itis an object of the invention to provide a mufiler that is very small inwidth and thickness but which incorporates a tri-fiow gas passage and toprovide a tri-flow gas passage for mufilers which has improved soundattenuating characteristics. The invention accomplishes the foregoingand other objects by means of a construction in which a combination oflongitudinal and transverse partitions act along with the side Walls ofthe mutller casing to define three separate gas passages through whichthe gas flows successively from the inlet at one end to the outlet atthe other end of the mufller. The partitions are preferably providedwith banks of louvers so that the central gas passage acts not only as aflow passage but as the volume into which the louvers open and throughwhich cross flow may occur to lower back pressure and attenuate sound byinterference.

Description of the drawings FIG. 1 is a longitudinal cross sectionthrough one form of muffler embodying the invention;

FIG. 2 is a cross section along the line 2--2 of FIG. 1;

FIG. 3 is a blank layout of one of the longitudinal partitions used inthe mufiler of FIGS. 1 and 2;

FIG. 3A is a blank layout of the other longitudinal partition used inthe muflier of FIGS. 1 and 2;

FIG. 4 is a longitudinal cross section through another form of mufflerembodying the invention;

FIG. 5 is a cross section along the lines 5-5 of FIG.

FIG. 6 is a blank layout of the longitudinal partitions used in themuffier of FIGS. 4 and 5;

FIG. 7 is a detail view of a transverse partition;

FIG. 8 is a side elevation of the transverse partition of FIG. 7;

FIG. 9 is a longitudinal cross section through another form of mutfierembodying the invention;

FIG. 10 is a cross section along the line 10-10 of FIG. 9;

FIG. 11 is a blank layout of the longitudinal partition forming means(in this case a tube) used in the muflier of FIGS. 9 and 10;

FIG .12 is a side elevation of a partition used to close the end of thetube of FIG. 11;

FIG. 13 is a side elevation of the partition of FIG. 12;

FIG. 14 is a side elevation of the partition used at the inlet end ofthe gas passages;

FIG. 15 is a side view of the partition used at the outlet or downstreamend of the tri-flow gas passages;

FIG. 16 is a schematic longitudinal cross section through amodification;

FIG. 17 is a schematic longitudinal cross section through anothermodified form of the invention;

FIG. 18 is a cross section along line 1818 of FIG.

FIG. 19 shows a method of forming the transverse and longitudinalpassages from one piece of metal; and

FIG. 20 shows a side elevation of an exhaust system utilizing themufiler of this invention.

Detailed description Referring now to the embodiment shown in FIGS. 1-3,the muffler 1 has a tubular sheet metal casing or housing 3 which isreduced in diameter at opposite ends to form an inlet bushing 5 and anoutlet bushing 7. The outer diameter of the casing 3 is preferably about3 inches, thus enabling the muffier to be advantageously used in modernautomobiles which have very little under-car space. Adjacent the innerend of the bushing 5 is an inlet chamber 11 and adjacent the inner endof the outlet bushing 7 is an outlet chamber 13. The inner end of theinlet chamber 11 is defined by a transverse partition 15 and the innerend of the outlet'bushing 13 is defined by a transverse partition 17.The partitions 15 and 17 are partly circular and have flanges 19 whichare spot-Welded or otherwise attached to the wall of easing 3.

Gas passing from the inlet chamber -11 to the outlet chamber 13 musttravel the distance between the partitions in 15 and 17 three times.Thus, the mufiler is a triflow unit. The gas follows a first or inletpassage 21 and then reverses its direction of flow to head back towardthe inlet end in an intermediate or central passage 23 and then reversesits flow again to flow through an outlet passage 25 to the outletchamber 13.

The walls of the passages 21, 23, and 25 are defined by a pair oflongitudinal partitions 27 and 29. The partition 27 acts with the sidewall of the casing 3 to define the inner side of the inlet passage 21.The partition 29 acts along with the other side wall of the casing todefine the outlet passage 25. The two partitions 27 and 29 definetogether opposite sides of the central passage 23.

The partition 27 is formed from an originally fiat piece of metal 27awhich is bent along the phantom lines that are shown in FIG. 3. It willbe noted that the transverse partition 15 is formed by bending thepartly circular section 31 at the left end of the blank 27a along theline 33 so that it is at right angles to the balance of the plate 27a.The flanges 19 are formed by bending the section 31 along the dottedline 35. The sides of the plate 270 are bent along the lines 3 7 and 39to form flanges 41 which extend longitudinally and are spotwelded to thewall of the casing 3 so that the partition 27 is held in the properposition. The end of the plate 27a has a reduced width flange 43 formedon it which is bent along the dotted line 45 at right angles to theplate.

The plate 29a of FIG. 3A, from which partition 29 is formed, is verysimilar to the plate 27a except that the parts are reversed so that oneis left-handed and the other is right-handed and it is somewhat widerthan plate 27a so that the side flanges 47 which are formed by bendingit longitudinally along the dotted lines 49 and 51 are wider than thecorresponding flanges 41. The plate 29a has a partly circular section 53which is bent along the dotted line 55 at right angles to the plate 29aso as to form the partition 17 The outer periphery of the section 53 isbent along dotted line 57 to form the flange 19 which may be spotweldedor otherwise suitably attached to the wall 3. The opposite end of theplate 29a has a reduced width flange 59 which is bent normal to theplate along the line at. The flange 59 is spotwelded to the transversepartition 15 whereas the corresponding flange 43 of the plate 27a isspotwelded to the partition 17.

The partition 27 has a relatively large area or bank 63 of fine flatlouvers 65 formed therein along with an opening 67 which forms a meansof interconnecting the passages 21 and 23 adjacent to the partition '17.Similarly, the partition 29 has a bank 69 of fine flat louvers 71 formedtherein and an opening 73 which is located adjacent to the partition 15so that the gas from passage 23 can flow into the passage 25.

In operation, the exhaust gas entering the inlet bushing flows into theinlet chamber 11 and from there into the longitudinal inlet passage 21.The mainstream of gas reverses direction as it flows through hole 67 andflows back toward the inlet through the central passage 23. It reversesdirection again as it flows through the opening 73 into the outletpassage 25 through which it flows to the outlet chamber 13 and then outof the mufller through the outlet bushing 7. In addition to themainstream of gas flow through the three longitudinal passages, there isa substantial transverse or cross flow of gas due to the open areasprovided by the louver banks 63 and 69.

FIGS. 4 to 8 show a modified form of the mufiier which is similar inmost respects to the embodiment shown in FIGS. 1 to 4, the principaldifference being that the transverse partitions are formed as separateparts and the two longitudinal partitions are identical in constructionto each other.

In the mutfler 101 of FIGS. 48, there is an outer shell or casing 103which is reduced in diameter at opposite ends to form an inlet bushing105 and an outlet bushing 107. Adjacent the inlet end of the inletbushing 105 is an inlet chamber 108 and adjacent the inner end of theoutlet bushing 107 is an outlet chamber 109. The inside ends of thechambers 108 and 109 are defined by transverse partitions 111 and 113,respectively, which are shown in detail in FIGS. 7 and 8. It will beseen that these are partly circular plates that have transverse flanges115 formed around their outer periphery whereby they may be spotweldedor otherwise suitably attached to the shell 103.

A pair of longitudinal partitions 117 and 119' divide the space betweenthe partitions 111 and 113 into three longitudinal passages throughwhich the gas must flow. There is the inlet passage 121 which receivesgases from the inlet chamber 108, a return flow or intermediate passage123, and an outlet passage 125 which delivers gases to the outletchamber 109. The partitions 117 and 119 are preferably identical inconstruction and formed from originally flat blanks such as shown inFIG. 6. Thus, the partitions have flanges 127 formed at opposite endswhich are bent around dotted lines 129 to positions at right angles tothe body of the partition, and these are preferably spotwelded to thetransverse partitions 111 and 113. Longitudinal flanges 131 are formedon opposite sides of the partitions 117, 119 by bending the outerportions about the lines 133 and 135. The flanges 131 are spotwelded tothe shell 103. The partitions 117, 119 have banks or patches 137 oflouvers 139-, preferably round, therein and each partition has anopening 141 which may be provided with a neck 143.

When the parts are assembled, as shown in FIG. 4, it will be seen thatthe operation of the muffler is substantially the same as thatpreviously described. The addition of the necks 143 about the openings141 will provide some tuning effect that helps to attenuate certain ofthe intermediate and low frequencies.

The embodiment shown in FIGS. 9-15 differs from the previous twoembodiments mainly in the structure for providing the two longitudinalpartitions. In this embodiment the partitions are formed by one piecewhich is rolled up into a tubular form and then attached to thetransverse partitions at opposite ends.

The mufller 201 of FIGS. 9-15 has an outer shell 203 which is reduced indiameter at opposite ends to form an inlet bushing 205 and an outletbushing 207. Adjacent the inner end of the inlet bushing 205 is an inletchamber 209 and adjacent the inner end of the outlet bushing 207 is anoutlet chamber 211.

At the inner end of the inlet chamber 209 is a transverse partition 213of the configuration shOWn in FIG. 14 and which has a peripheral flange215 that is spotwelded to the outer shell 203. At the inner end of theoutlet chamber 211 is a transverse partition 217 of the configurationshown in FIG. 15 which also has an outer peripheral flange 219 that isspotwelded to the outer shell 203.

Extending between and secured to the partitions 213 and 217 is a tube221 of relatively flat elliptical cross section so that it has a bottomsection 223 and a top section 225. As can be seen from FIG. 11, the tube221 is formed from an originally flat metal blank 227 which is rolledinto the elliptical configuration. The blank 227 is substantially acomposite of the two partitions used in the preceding embodiments withthe attaching flanges removed. Thus, the bottom section of the blank 227has a bank 229 of fine flat louvers 231 and also an opening 233. The topsection of the blank 227 has a bank 235 of fine flat louvers 237 and anopening 239 in it. When the blank 227 is rolled into tubular form, thedownstream end 241 fits on and is spotwelded to an elliptically shapeddepression 243 that is formed in the partition 217. The upstream end 245of the tube 221 fits inside of an elliptically shaped neck 247 formed inthe partition 213. It is closed by an elliptically shaped partition 249(FIGS. 12 and 13) which has a peripheral flange 251 whereby it may bespotwelded inside the end 245 of the tube 221 and to the neck 247.

In operation of tr e muffler 201, exhaust gas enters the inlet bushing2G5 and flows into inlet chamber 209 from which it flows through opening253 in partition 213 into the longitudinal inlet passage 255. A mainstream of the gas reverses direction at the end of passage 255 as itflows through the opening 233 into the central longitudinal pas sage257. It then reverses direction at the end of passage 257 as it flowsthrough opening 239 into the longitudinal outlet passage 259, from whichit flows into outlet chamber 211 through opening 261 in partition 217and then into the outlet bushing 207. A cross flow of gas cuts acrossthe longitudinal passages, especially passage 257, due to the open areasprovided by the louver banks 229 and 235 in combination with thoseprovided by the openings 233 and 239.

In the several embodiments of the invention described above, soundenergy is eflectively removed from the gas by various means contained ina minimnm size muflier. Energy is abstracted from the gases as theyenter and leave the inlet and outlet chambers due to the abrupt changesin cross section of the areas through which the gas flows. While thebanks of louvers could in the broad purview of the invention be replacedby mere perforations, louvers are preferred since they act as shorttuning necks to attenuate high frequency sounds in the gases flowing bythem. The relatively long length of the gas passage due to the tri-flowconstruction also provides for maximum sound attenuation.

Of major importance in the sound removal capabilities of mufilersembodying the invention is the substantial cross flow of gas from theinlet passage to the outlet passage across the intermediate passage. Dueto the confining effect of the outer housing and the common perforatedwalls shared by the three passages, all gas that attempts duringfavorable pressure pulse conditions to by-pass from the inlet passage isformed to enter or cut entirely across the intermediate passage. Thiscross flow causes enough acoustic interference to collapse troublesomenotes or waves. Preferably, the louver banks extend across substantiallythe entire width of the partitions and along a large portion of theirlengths as shown in the three embodiments. Excellent results have beenobtained when the total open area of each louver bank was the same andthis area was substantially the same as the cross-sectional area of theinlet passage. The louver bank area, especially the one opening into theinlet passage, is preferably about 35-60% of the cross-sectional area ofthe inlet passage. Preferably, the muffler is positioned in the exhaustsystem so that the louver bank in the inlet passage is located adjacenta pressure peak or antinode of any special frequency it is desired tohave the mufiler attenuate.

While the heights of the three passages seen along a diameter of thecasing may be of the proportions shown, itis feasible to reduce theheight (decrease the area) of the central passage because of the crossflow direct from the inlet to the 'outlet passage. Preferably, however,the cross-sectional area of the central passage is substantially larger,e.g., two or three times, than that of the inlet passage and preferablyalso substantially larger than that of the outlet passage. When thisrelationship is used, the velocity of gas flow through the centralpassage is materially less than it is in the smaller area passages andmaterially less than that of the cross flow gases, thus promotingmaximum interference and turbulent effects. It can be seen that bylocating the central passage along the midsection of the casing (whichcould be oval as well as round) the central passage will have a muchlarger width and area than the inlet and outlet passages even though itsheight is the same or even somewhat less thereby facilitating cross flowof gases from the inlet passage "all the way to the outlet passage andpromoting maximum attenuation.

In addition to the sound attenuation caused by cross currents of gasflow into and/or through the main flow stream along the central passage,sound attenuation occurs because the central passage acts as a volumeinto which the louvers open so that sound waves from the main stream canenter it and be trapped or dissipated. The central passage thereforeacts'in a plurality of distinctly different acoustic ways to attenuatesound.

Additional acoustic uses of the central passage are possible as seenschematically in the muffler 301 of FIG. 16. This muffier has an outercasing 303 which acts with the longitudinal partitions 305 and 307 andthe transverse partitions 309 and 311 to define the longitudinal inletpassage 313, the central passage 315, and the outlet passage 317. Thepartitions 305 and 307 have mainstream flow openings 319 and 321 andlouver banks 325 and 326 all as described in the preceding embodiments.It will be noted, however, that in this embodiment the openings 319 and321 are located a substantial distance inwardly of the ends of thecentral passage 315 thereby providing dead end chambers 327 and 329 atopposite ends of the central passage. Corresponding dead end chambers331 and 333 are formed at the downstream and upstream ends,respectively, of the inlet and outlet passages 313 and 317. v

In operation of the muffler 301 of FIG. 16, the gas flow and soundattenuation occurs as in the preceding embodiments. Additionally, thechambers 327, 329, 331 and 333 act as sound absorbing dead chamberswhich, if of the proper volume and/or length, act to attenuate certainnotes in the exhaust gas sound spectrum. If desired, a tuning neck 335may be attached to a partition 337 placed in the central passage 315 toserve as a means acting with the chamber 329 to tune it to a desiredfrequency. Also, if desired, the partition 305 may be provided with abank of louvers 338 that open into the chamber 327. Thus, the deadchamber 327 will act in conjunction with these louvers to some extent asa spit chamber for removing high and medium frequency sounds.

FIGS. 17 and 18 show a modification in which a muftier similar to themufiler 1 is used inside of an outer casing. The space between thismuflier and the outer casing is then used as additional silencing means.

Thus, the muflier 401 of FIG. 17 has an internal trifiow mufiier 403.The casing 405 of the mufiler 403, which may be the same as the casingsof the mufflers previously described, is disposed inside of the casing407 and the inlet and outlet bushings 409 and 411 may be disposed insideof and spotwelded to one or both of the inlet and outlet bushings 413and 415 in the inlet and outlet headers 417 and 419 attached to the endsof the casing 407 in a conventional manner. As seen in FIG. 18, thecasing 407 may be elliptical and tangent to the top and the bottom ofthe casing 405, as indicated at the lines 421 and 423. The inner andouter casings 405 and 407 may be welded together along theselongitudinal lines of contact to divide the space between them into twotransversely separated, longitudinally extending chambers 425 and 427.These two chambers may, if desired, be additionally subdivided bytransverse partitions into longitudinally separated chambers as, forexample, by a partition (not shown) located on the section line 18-18.Inside of the casing 405 are a pair of longitudinal partitions 429 and431 and a pair of transverse partitions 433 and 435 which divide thespace inside of the casing 405 into an inlet passage 437, a centralpassage 439, and an outlet passage 441, all as previously described inconnection with the other embodiments of the invention. The opening 443permits gases to flow in a main stream from the inlet passage 437 to theintermediate passage 439 while the opening 445 in partition 431 permitsgases to flow in a main stream from the central chamber 439 to theoutlet chamber 441. The louver patches 447 and 449 in the longitudinalpartitions 429 and 431 permit the cross-flow of gases as previouslydescribed. The wall of the casing 405 is provided with a louver patch451 which opens into the outlet passage 441 and connects it with thelongitudinal chamber 425. Thus, the chamber 425 acts as a large spitchamber or untuned resonator to attenuate a broad spectrum ofintermediate and high frequencies remaining in the gases as they passthrough the passage 441. It will be noted that the louver patch 451could be provided if desired to open into one or more of the threelongitudinal passages, either alone or in combination. The illustrateddesign however is preferable to preserve maximum crossflow across thecentral passage.

The mufiier 403 has an inlet chamber 453 and an outlet chamber 455 as inthe preceding embodiments and in accordance with this embodiment one orthe other of these chambers, such as chamber 453, is provided with atuning neck 457 which forms the only inlet and outlet to the chamber427. By proper sizing of the length and area of the neck 457 incombination with the volume of the chamber 427 the two can be used totune to a desired medium or low frequency.

FIG. 19 shows how a one-piece stamping 501 may be rolled up as indicatedat 503 into the construction 505 which will provide both thelongitudinal and transverse partitions to form the three longitudinalpassages as described above.

It will be noted that what have been referred to as the longitudinalpassages formed by the longitudinal partitions serve more broadly aslongitudinal sound attenuating chambers through which the mainstream ofgas follows a tri-fiow passage through the mufiler. The gas in eachpassage of the mainstream, however, is in acoustic connection throughthe banks of louvers with the adjacent chamber which acts to attenuatesound in the mainstream gas. The banks of louvers also act as openingsto permit cross-flow of the gas that does not remain in the main gasstream following the tri-flow passage.

FIG. 20 shows the muffler of this invention incorporated into an actualexhaust system, the illustrated system being one designed to silence theexhaust of a 1965 Citroen DS19. The exhaust system shown in FIG. 20comprises a relatively long broad banded, resonator chamber unit 601having an inlet end 603. At the outlet end 605 a connecting pipe 607 isattached and this is bent as indicated in the drawings and itsdownstream end is attached to the inlet end of a mufiier 609 which maybe any one of the muftlers previously described but is preferably themufiier 101 shown in FIGS. 4-8. At the outlet end of the muffler 609there is a connecting pipe 611 which is bent as shown and attached tothe inlet end 613 of a spit chamber unit 615. The outlet end of the 615is inserted in the inlet bushing 617 of a tuned silencer 619 and atailpipe section 621 attached to the outlet 623 of the silencer 619carries the gases to atmosphere. The various conduits or pipe scetions,such as 6-07 and 611, are one and one-half inch in outer diameter Whilethe various silencing devices are of three inch outer diameter. Itdesired, the devices other than the tri-fiow unit 609 may be flattenedto reduce their Width in one dimension and to give them a somewhat ovalconformation.

The silencing device 619 has an outer casing while is preferably pincheddown at 625 to the inner pipe 627 so as to divide the easing into arelatively long chamber 629 and a somewhat shorter chamber 631. The pipe627 is louvered along the length of the chamber 631 so that it forms anuntuned resonator chamber. The louvers extend along preferably about 12%inches of the pipe and the full length of the chamber. The pipe section627 in the chamber 62.9 has a louver patch 633 which is preferablylocated as indicated and about 5 inches long. The balance of the chamber629 upstream from the louver patch 633 is preferably 34 inches long. Thelouver patch 633 is preferably located 35 inches from the downstream endof the tailpipe section 631. This is the anti-node of a 125 cyclestanding wave to which the chamber 629 is tuned.

The spit chamber 6-15 has a housing 637 which provides a chamber 639around the inner pipe 641 which is louvered along substantially its fulllength, approximately 7 /8 inches, so that the chamber 639 will act as aspit chamber or untuned resonator to attenuate medium and highfrequencies.

The action of the mufiler 609 has already been described in connectionwith the various embodiments of the invention and in this particularexhaust system it acts, without imposing undue back pressure, tosubstantially lower the sound level and to substantially attenuatestanding waves occurring at 75 and 175 cycles. The unit 609 ispreferably about 14 inches long exclusive of the inlet and outletbushings, and the longitudinal tri-flow passages are preferably about 7%inches long.

The untuned resonator unit 601 has a housing 643 around the interiorpipe 645 to provide a chamber 647. Louvers extend along the full lengthof the chamber or about inches of the pipe 645 to open into chamber 647which acts, therefore, as a spit chamber and untuned resonator toattenuate medium and high frequencies.

It will be noted in the exhaust system of FIG. that the mufiier 609,which itself is of relatively simple construction, does such asubstantial job of sound attenuation that it is possible to make therest of the system of extremely simple construction and of very smallouter dimension.

The tri-flow mutllers illustrated herein embody a variety of effectivesilencing principles and techniques in a small, economical constructionthat has low back pressure. In manufacture the metal partition meanswhich subdivides the interior of the casing into the various chambersmay be inserted into an open ended metal tube and spot-Welded to it andthen the ends of the tube swaged down to form the actual casing havingthe inlet and outlet bushings illustrated.

Modifications may be made in the structure illustrated without departingfrom the spirit and scope of the invention.

I claim: 1. An exhaust system for silencing the exhaust gase of aninternal combustion engine and having standing waves of substantially75, 125, and 175 cycles per second comprising in succession going fromthe upstream end of the system to the downstream end of the system: anuntuned resonator and spit chamber unit, a first conduit connected toand receiving gas from said unit, a tri-fiow muffler connected to andreceiving gas from said first conduit, said tri-fiow muffler having acasing with a pair of internal partitions subdividing the casing intothree laterally adjacent and tri-flow connected gas flow chambers andbeing perforated to provide for cross flow between the chambers, saidtri-flow mutfier lowering the sound level in said system and attenuatingsaid and 175 cycle Waves, a second conduit connected to receive gas fromsaid tri-fiow muffler, a second untuned resonator and spit chamberconnected to and receiving gas from said second conduit, 21 tunedsilencer connected to and receiving gas from said second untunedresonator and tuned to attenuate said cycle wave, said tuned-silencerincluding a center tube and a casing providing a chamber around saidcenter tube and said chamber being closed except for a bank of louversprovided in said center tube and which is located substantially at ananti-node of said 125 cycle wave, a third untuned resonator and spitchamber receiving gas from said tuned silencer, and a tailpipe conduitreceiving gas from said third untuned resonator and discharging it toatmosphere.

References Cited UNITED STATES PATENTS 2,043,030 6/1936 Bourne 181592,111,537 3/1938 Noblitt et al. 181-61 2,297,046 9/1942 Bourne 181592,367,753 1/1945 Buck 18135 3,036,654 5/1962 Powers 18154 3,196,9767/1965 Powers et al. 18161' XR 3,219,142 11/1965 Deremer 181- 61 XRFOREIGN PATENTS 854,651 1/ 1940 France. 1,060,334 11/1953 France.1,351,921 12/1963 France.

341,156 1/1931 Great Britain.

892,780 3/1962 Great Britain.

ROBERT S. WARD, ]R., Primary Examiner.

